Apparatus for electrostatic image-forming and processes for use therewith

ABSTRACT

An electron beam tube for use in formation and recordation of electrostatic charge patterns has a face plate including a photoconductive layer and a conductive base which is transmissive to electron beams and is disposed intermediate the photoconductive layer and the tube electron beam emitter. Processes for forming electrostatic charge patterns in such face plate include the steps of placing an insulative charge-retaining layer in contact with the photoconductive layer, the insulative layer either being previously charged or being charged while in position on the photoconductive layer, and applying a voltage to the face plate and simultaneously irradiating the photoconductive layer with pattern-indicating electron beams. Electrostatic charge patterns thus-formed in the insulative layer may be developed in place or transferred and subsequently developed.

United States Patent Inoue et al. 1 June 27, 1972 [54] APPARATUS FORELECTROSTATIC 3,196,011 7/1965 Gunther ..96/1 PC RMIN 4ND 3,234,0192/1966 111111 IMAGE-F0 G PROCESSES 3,458,752 7/1969 Stowell ..346/74 EBFOR USE THEREWITH Inventors: Elichi Inoue; 'Keizo Yamaji; HiroshiTanaka; Takashi Saito, all of Tokyo, Japan Canon Camera KabushikiKaisha, Tokyo, Japan Filed: Feb. 20, 1969 Appl.No.: 800,961

Assignee:

Foreign Application Priority Data Feb. 27, 1968 Japan ..43/l2741 11.5.C1. ..346/74 ES, 96/1 PC, 101 1310. 13, 250/495 zc, 346/74 EB 1111.0...G03g 13 22, (303g 15/22 Field 61 Search ..346/74 ES, 74 EB; 101 010.13; 96/1 R, 1 PC, 1 c; 250 495 c, 49.5 zc

References Cited REFERENCE OSCILLATOR Primary Examiner-Howard W. BrittonAttorneyWatson, Leavenworth and Kelton ABSTRACT An electron beam tubefor use in formation and recordation of electrostatic charge patternshas a face plate including a photoconductive layer and a conductive basewhich is transmissive to electron beams and is disposed intermediate thephotoconductive layer and the tube electron beam emitter. Processes forforming electrostatic charge patterns in such face plate include thesteps of placing an insulative chargeretaining layer in contact with thephotoconductive layer, the insulative layer either being previouslycharged or being charged while in position on the photoconductive layer,and applying a voltage to the face plate and simultaneously irradiatingthe photoconductive layer with patternindicating electron beams.Electrostatic charge patterns thus-formed in the insulative layer may bedeveloped in place or transferred and subsequently developed.

27 Chins, 16 Drawing Figures CIRCUIT DIN P'ATENTinJunz'r m2 sum 2 or 4FIGS FIG.7

FIG. '10

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PATENTEnJum m2 3.673.595 sum aor 4 PROCESSING STATION 49 so 47PKTENTEnJum m2 7 Y 3.673.595

EET u 0F 4 FIG. 13

'36 I 58 13 3. H 12 15 CRT NF "I 59 \i Ill 333%? 4 43 oron 42 MEM0R4Y3 4i A a DELAY CIRCUIT APPARATUS FOR ELECTROSTATIC IMAGE-FORMING ANDPROCESSES FOR USE THEREWITH The present invention relates toelectrostatic recording and more particularly to electron tubes having aphotoconductive member incorporated in the face plate thereof and toprocesses for use of such tubes in forming and recording electrostaticcharge patterns in response to information signals.

Various methods are known for electrostatically recording informationsignals. For example, in the method disclosed in U.S. Pat. No. 2,879,422issued to H.C. Borden et a1., a cathode ray tube is utilized having aface plate composed of conductive pins electrically insulated from eachother and embedded in an insulative layer in the form of a matrix.Information signals are converted into electron beams by a cathode raytube and the electron beams are passed through said pin conductors so asto cause gaseous discharge in a recording member, thereby formingelectrostatic charge patterns on the recording member. In this methodthe density of conductor pins in the matrix significantly influencesresolution. Since it is extremely difficult to arrange conductor pins ina desired high density in the matrix because of the construction of theface plate, the formation of electrostatic charge patterns having highresolution is impossible. Furthermore, in this method, electrostaticcharge patterns are formed .by atmospheric discharge. Thus,pattem-forming discharges are greatly influenced by environmentalconditions, and discharges may thus tend toward instability, therebydisturbing the indicated patterns or images. In addition, it isdifficult to obtain high contrast electrostatic charge patterns by thismethod.

Another known method is disclosed in US. Pat. No. 3,132,206 issued toP.F. King. According to his method, information signals are firstconverted into fluorescent images upon the face plate of a cathode raytube and such images are utilized as light images forelectrophotographic recording in accordance with the Carlson process,i.e., projecting the images upon a xerographic plate to formelectrostatic charge patterns on the photoconductive layer ofsaid,plate. In this method, it is required that the photoconductivematerial have a relatively high resistance in order to retain thecharges on the photoconductive layer. Therefore it is very difficult toemploy highly sensitive photoconductive material having a relatively lowresistance so that the sensitivity of this method is low and anelectrostatic charge pattern having high contrast is not formed.Furthermore, according to this method the information signals areconverted into light images and thereafter these light images areelectrostatically recorded so that both efficiency and speed areinferior.

An object o f the present invention is to eliminate the above-describeddisadvantages in known conventional methods by providing a novelelectrostatic recording tube and electrostatic charge pattern-formingand recording processes.

Specifically, an electrostatic recording tube according to the presentinvention has electron beam generating means, means for emitting saidelectron beams upon a face plate and other means incorporated inconventional electrostatic recording tubes. The novel face plate of thepresent invention has one fundamental arrangement including two layers,a thin layer electrode transmissive to electron beams and aphotoconductive layer. Another fundamental face plate arrangementincludes three layers, a thin layer electrode of the type describedabove, a photoconductive layer and a chargeretaining insulative layer.Furthermore, an airtight layer and any other suitable additional layersmay be incorporated in the face plate, if required. The face plate ofthe present invention responds effectively to single or simultaneousemission of electron beams, voltage application and/or emission ofradiation so that high contrast electrostatic charge patterns may beformed upon the surface of the face plate or on a recording memberoverlaid thereupon according to recording processes which will bedescribed in detail hereinafter.

In order to form electrostatic patterns upon the surface of the faceplate, one fundamental recording process of the present inventioncomprises the steps of: maintaining the surface of the face plate of theelectrostatic recording tube of the present invention at a predeterminedpotential level; emitting electron beams through the thin layerelectrode upon the photoconductive layer while simultaneously applying avoltage to the face plate; and illuminating the photoconductive layerwith blanket radiation to which the photoconductive layer is sensitive.

Another fundamental recording process of the present invention comprisesthe steps of: maintaining the face plate at a predetermined potentiallevel; thereafter contacting closely thereupon a recording member orcontacting closely upon the face plate a recording member which ispreviously maintained at a predetermined potential level or maintainingthe face plate at a predetermined potential level with the overlyingrecording member in place; emitting electron beams through the thinlayer electrode upon the photoconductive layer while simultaneouslyapplying a voltage to said recording member; and thereafter removing therecording member from the face plate or illuminating the photoconductivelayer with blanket radiation to which the photoconductive layer issensitive, thereby forming electrostatic charge patterns upon therecording member.

Recording processes of the present invention may include the furthersteps of rendering visible the thus-formed electrostatic charge patternsby suitable means and manner such as coloring, frost, etc. so as todirectly obtain permanent images for storage, and/or transferring theelectrostatic charge patterns, as they are formed or visualized, to acopying member for further processing.

As described above, according to the present invention, the face plateincorporating the photoconductive layer is directly or indirectlymaintained at a predetermined potential level and electron beams areemitted upon the face plate, over which is laid a charge-retaininginsulative layer, while simultaneously applying a voltage to the faceplate. By the interactions among the initial potential, the electronbeams and said applied voltage, with or without the emission of blanketradiation, the electron beams controlled by image-defining signals areconverted into electrostatic charge patterns for recording.

According to the present invention, the electron beams controlled by theimage-defrning signals can be directly recorded as electrostatic chargepatterns upon the charge-retaining insulative layer at high speed,thus-formed patterns being stable and having high contrast andresolution. One of the salient features of the present invention is thatthe recording process can be carried out even in ambient light.

One of the objects of the present invention is to provide a novel andimproved electrostatic recording system.

Another object of the present invention is to provide an improvedelectrostatic recording tube, the face plate of which incorporates aphotoconductive layer.

Another object of the present invention is to provide an improvedrecording tube for the formation of electrostatic charge patterns uponthe face plate thereof.

A further object of the present invention is to provide an improvedrecording tube having means for applying blanket radiation to the faceplate thereof.

A still further object of the present invention is to provide animproved recording tube for recording electrostatic charge patternsderived from electron beam signals controlled by information signals.

Another object of the present invention is to provide an improvedelectrostatic recording process comprising the steps of emittingelectron beams upon a face plate incorporating therein a photoconductivelayer while simultaneously applying a voltage thereto, thereby recordingthe electron beam signals in a charge-retaining member as stableelectrostatic charge patterns having high resolution and high contrast.

An additional object of the present invention is to provide an improvedrecording process permitting the formation of high contrastelectrostatic charge patterns even in ambient light.

A yet further object of the present invention is to provide an improvedrecording process for recording electron beam signals as permanentelectrostatic charge patterns.

The above and other objects, advantages and features of the presentinvention will become apparent from the following description taken inconjunction with the accompanying drawings.

FIGS. la-lc show sectional views of face plates for electron tubes inaccordance with the present invention.

FIGS. 2, 3 and 4 illustrate the principles of an electrostatic chargepattem-forming process of the present invention.

FIGS. 5 to 11 are explanatory views illustrating the principles ofanother electrostatic charge pattern-forming process of the presentinvention.

FIG. 12 is a schematic view illustrating the structure of a recordingtube of the present invention and associated apparatus used in arecording process in accordance with the invention.

FIGS. 13 and 14 are schematic views illustrating apparatus used in otherelectrostatic charge pattem-forming and recording processes inaccordance with the present invention.

FIG. 1 is an explanatory view illustrating fundamental structures offace plates for electrostatic recording tubes of the present invention.Referring to FIG. la, on charge-retaining insulative layer 1 is formedphotoconductive layer 2 applied by spraying, coating, vacuum depositionor the like. Upon photoconductive layer 2 is formed thin layer electrode3 by vacuum deposition or the like. Thus, the face plate is composed ofthree fundamental layers, charge-retaining insulative layer 1,photoconductive layer 2 and thin layer electrode 3.

FIG. lb illustrates another face plate according to the presentinvention. This-face plate is fundamentally composed of four laminatedlayers, that is, airtight layer 4 formed on the cathode ray tube inorder to maintain a high degree of vacuum therein, thin layer electrode3 formed by vacuum deposition or the like upon airtight layer 4,photoconductive layer 2 formed upon layer 3 by coating,vacuum-deposition or the like and charge-retaining insulative layer 1formed upon photoconductive layer 2.

FIG. 1c illustrates another face plate according to the presentinvention similar to that shown in FIG. 1a with the exception that thereis not charge-retaining insulative layer 1. This face plate is composedof thin electrode layer 3 and overlying photoconductive layer 2. It isof course possible to provide an airtight layer 4 overlying thinelectrode layer 3 as in the face plate shown in FIG. lb. Furthermore, acharge control layer may be interposed between thin layer electrode 3and photoconductive layer 2, and a layer for binding electric charges orany other suitable layer may also be formed upon or adjacent to theinterface between photoconductive layer 2 and the insulative layerwithout adversely affecting the im' roved operation and effects ofrecording processes of the present invention.

Any material having high resistance to abrasion, relatively highelectrical resistance and adapted to retain electric charge may be usedfor the insulative layer. The insulative layer material may betransparent or non-transparent to radiation to which photoconductivelayer 2 is sensitive. Such insulating materials are, for example,macro-molecule films such as polyester resin, polypropylene resin,polycarbonate resin, polyethylene resin and other resins, glass, ceramicor the like coated with A1 SiO and other inorganic materials and saidmaterials may be rendered nontransparent. Preferably thecharge-retaining insulative layer is composed of one of or a mixture ofthe above materials or a lamination thereof and has a thickness from to50 .1..

Materials for the photoconductive layer are: Se, S, SeTe, CdS, CdSe andother chalcogenide compounds; photoconductive metal oxides such as ZnO,PhD and so on; inorganic photoconductive materials; and organicphotoconductive materials such as antracene compounds, carbazoles, etc.A single coating of photoconductive material as described above may beused and a binding agent may be added thereto or mixtures of the abovedescribed materials may be used. Altematively, laminates may be used.The thickness of the photoconductive layer is preferably less than 200u.

Thin layer electrode 3 is used as the anode of the electrostaticrecording tube and serves as an opposing electrode when a voltage isapplied to the face plate so that charges may travel between the thinlayer electrode and the photoconductive layer. Materials for thin layerelectrode 3 must satisfy these operating conditions and may be composedof a transparent conductive material, such as Au or the like having athickness of approximately A, an opaque thin layer having a thickness of1,000 to 10,000 A or other conductive thin layers depending upon theapplication.

Airtight layer 4 maintains a high degree of vacuum in the electrostaticrecording tube and serves as an auxiliary reinforcing member for theface plate. The use of this airtight layer causes the electron beams tobe partially adsorbed, thus reducing the efliciency of the recordingtube, but this inefficiency is offset by advantageous maintenance of ahigh degree of vacuum in the recording tube. For example, a metallicthin layer or the like about 1 p. in thickness reinforced by mica ormosaic-shaped grating a few microns in thickness may be used.

For joining the layers, various kinds of binders and adhesives may beused. Satisfactory results can be attained by the use of epoxy resinseries adhesives, polyester resin series adhesives, other polymeradhesives or varnish in which vinyl chloride, vinyl acetate copolymer,polyvinyl alcohol or the like is dissolved in a solvent.

The process for forming electrostatic charge patterns according to thepresent invention will now be described. FIGS. 2 to 11 schematicallyillustrate processes for forming electrostatic charge patterns accordingto the present invention and the states of charges in each step of theprocesses. First, the process practiced upon the face plate shown inFIG. la will be described with reference to FIGS. 2 through 4. In thefirst step, the face plate is provided with a predetermined potential asshown in FIG. 2, and in the second step, electron beams 8 are directedupon photoconductive layer 2 through thin layer electrode 3 andsimultaneously a voltage is applied to the face plate as shown in FIG. 3so that an electrostatic charge pattern is formed as shown in FIG. 3.Furthermore, blanket radiation L to which photoconductive layer 2 issensitive is directed thereupon, thereby forming a high contrastelectrostatic charge pattern on charge-retaining insulative layer 1 ofthe face plate as shown in FIG. 4.

As shown in FIG. 2, in darkness or in light, insulative layer I ischarged by corona discharge device 5 or any other suitable well knownmeans such as an electrode roller, a friction charging means or thelike, connected to a high voltage source (not shown). In this case, thinlayer electrode 3 is grounded at as 6. Thus, a predetermined potentialis maintained across the face plate, a negative potential level in thiscase.

When the surface of the insulative layer is charged positively, chargesof opposite polarity will be bound at the interface between insulativelayer 1 and photoconductive layer 2 or adjacent thereto. These chargesare composed of free carriers, photocarriers in photoconductive layer 2,or carriers injected from the thin layer electrode or a mixture thereof.Such charges will be bound either in darkness or in light. Even if thecharges upon the surface of insulative layer I are removed and the layeris in darkness, the bound charges remain unchanged.

Next, as shown in FIG. 3, electron beams 8 corresponding to informationsignals are directed to photoconductive layer 2 through thin layerelectrode 3 from the inside of the electrostatic recording tube. In thiscase, by means of a well known suitable charging means such as coronadischarge means 7 or an electrode roller friction charging means whichis connected to a high voltage source (not shown), a voltage of polarityopposite to that of said charges, i.e., a positive voltage in this case,is simultaneously applied to insulative layer 1.

When photoconductive layer 2 has p-type conductivity, it is preferableto initially charge the surface of insulative layer 1 negatively andthen to charge the surface positively when electron beams are applied tothe photoconductive layer.

When the electron beams and said voltage are simultaneously applied tothe photoconductive layer, photoconductive layer 2 of the face platemust be shielded from ambient light. For this purpose, insulative layer1 may be rendered nontransparent to radiation to which photoconductivelayer 2 is sensitive. Alternatively, the shielding plate of chargingmeans 7 may be made of non-transparent materials or may be provided withextensions along both sides thereof as shown at 7. Alternatively, anyother means suitable for shielding the face plate from ambient light maybe provided, or the process of forming electrostatic patterns may beconducted in a darkroom.

When application of the voltage to insulative layer 1 and exposure ofphotoconductive layer 2 to electron beams occur simultaneously, chargesinitially provided on the surface of insulative layer 1 are dischargedless at dark portion D of photoconductive layer 2 because of thepositive charges bound therein. On the other hand, at exposed portions Lwhere electron beams are incident upon photoconductive layer 2, carriersare produced whereby the resistance of these portions of thephotoconductive layer is decreased, and thereby the bound charges areeasily released. Consequently, negative charges upon the insulativelayer surface corresponding to portions L of photoconductive layer 2 aresubstantially discharged by the negative polarity corona so that theseportions of the surface of the insulative layer are positively chargedwhereby electrostatic charge patterns corresponding to the signalsapplied are formed as shown in FIG. 3.

In this case, the thus-formed pattern would be adversely affected ifcarriers generated by electron beam excitation disperse inphotoconductive layer 2. But most of such carriers are considered tomove in the direction of the electric field due to bound charges, thatis in the direction perpendicular to the surface of and transversely ofthe thickness of the photoconductive layer. Therefore, the thickness ofphotoconductive layer 2 may be suitably arranged such that the resultingelectrostatic charge patterns are not adversely affected in practice.

Next, as shown in FIG. 4, radiation to which photoconductive layer 2 issensitive is directed thereupon uniformly. At this time, portions L onwhich electron beams were incident remain unchanged while the highresistance of portion D, on which less electron beams were incident inthe previous step, is rapidly reduced and portion D becomes conductive.Consequently, the charges bound at the interface between insulatinglayer 1 and photoconductive layer 2 or adjacent thereto disappear exceptthose charges bound by charges which remain on the surface of theinsulative layer. This state of the charges is shown in FIG. 4 and itwill be seen that an electrostatic pattern having contrast higher thanthat formed in the previous step is formed upon insulative layer 1.

The uniform or blanket radiation used in this step is selected inaccordance with the properties of the photoconductive layer, and forexample visible light rays radiated from the sun, tungsten lamps,fluorescent lamps, etc., ultraviolet rays, infrared rays, X-rays and anyother radiation may be used. The radiation is not limited to thedirection shown, i.e., from the transparent insulative layer side, asshown in FIG. 4, but may be transmitted from inside of the electrostaticrecording tube, that is through thin layer electrode 3, when theelectrostatic recording tube has a radiation emission means as will bedescribed in more detail hereinafter.

When this method is employed, the above described process can bepracticed even in the light by rendering insulative layer 1non-transparent to the blanket radiation. Thus-formed electrostaticcharge patterns may be transferred to another insulative copying memberfor storage or preservation. Altematively, electrostatic charge patternsupon the face plate may be developed by well-known electrophotographicmethods, such as the magnet brush method, the cascade method, the farbrush method, the spray method or the liquid processing method, etc. andthen may be transferred to a copying member. Thereafter, the face platemay be cleaned by any suitable method such as brushing the face platewith a fur brush, etc. well known in the art of electrostaticphotography. The face plate may thus be used repetitively.

It should be noted that in the above-discussed process, a positive ornegative pattern may be produced as needs demand. Furthermore, accordingto the present invention it is not necessary to directly charge thephotoconductive layer as in the case of conventional electrostaticphotographic processes. As described hereinabove, in the presentinvention the charge-retaining insulative plate is charged initially sothat charges provided upon the insulative layer may bind charges ofopposite polarity at the interface between photoconductive layer 2 andinsulative layer 1 or adjacent thereto so that not only high resistancephotoconductive materials, which are required in conventionalelectrophotography, but also relatively low resistance and highlysensitive photoconductive materials may beused in the present invention.Therefore, highly sensitive and high contrast electrostatic chargepatterns may be formed because of such highly sensitive photoconductivelayer and the unique pattern-forming processes of the present invention.

The process for forming electrostatic charge patterns upon the faceplate shown in FIG. 10 will now be described with reference to FIGS. 5through 1 1. In operation, insulative layer 1 is charged with apredetermined polarity as shown in FIG. 5 and in the second stepinsulative layer 1' is placed in close contact with photoconductivelayer 2 of the face plate so that the face plate may be maintained at apredetermined potential level as shown in FIG. 6. In the third step,electron beams 8' are emitted through thin layer electrode 3 uponphotoconductive layer 2 while a potential is simultaneously applied tothe face plate as in FIG. 7, thereby forming the electrostatic chargepattern shown in FIG. 7. Thereafter, in the fourth step, blanketradiation 9' is directed upon photoconductive layer 2 as shown in FIG. 8or insulative layer 1 is removed from photoconductive layer 2 of theface plate as shown in FIG. 10. In the final step, electrostatic chargepatterns are formed upon insulative layer 1' as shown in FIGS. 9 and 11.

The above-described process will now be described in more detail. First,in darkness or in light, both surfaces of layer 1 are provided withopposite polarity charges by any suitable wellknown means such as adouble corona discharger, electrode roller friction charging means, etc.Thus, insulative layer 1' is uniformly electrically charged as shown inFIG. 5. Next, the thus-charged insulative layer is placed in closecontact with photoconductive layer 2 of the face plate so that the faceplate is maintained at a predetermined potential, a negative potentialin this case. Thus, the face plate is electrically charged as shown inFIG. 6 in similar manner to the charging described in thefirst-discussed embodiment of the pattem-forming process of the presentinvention. Then, as shown in FIG. 7, electron beams 8' corresponding tothe information signals are directed upon photoconductive layer 2through thin layer electrode 3 from inside the electrostatic recordingtube. Concurrently, by means of any suitable charging means such ascorona discharge means 7 or the like connected to a high voltage ACsource (not shown), AC voltage is applied to insulative layer 1'. Inthis case, photoconductive layer 2 of the face plate must be shieldedagainst ambient light rays when electron beams are directed upon thephotoconductive layer and AC voltage is applied to the face plate as inthe case of the above-discussed embodiment of the present invention.

In the next step, as shown in FIG. 8, radiation 9 to which thephotoconductive layer is sensitive is directed uniformly uponphotoconductive layer 2 and the face plate retains charge as shown inFIG. 8, having a high contrast electrostatic charge at portions notexposed to electron beams. Thereafter insulative layer 1' is removedfrom photoconductive layer 2 as shown in FIG. 9.

On the other hand, when insulative layer 1' is removed fromphotoconductive layer 2 as shown in FIG. 10 instead of irradiationthereof as shown in FIG. 8, insulative layer 1' retains the case whensaid radiation is employed.

In order to permanently preserve the electrostatic charge patternsformed upon insulative layer 1' as shown in FIGS. 9 and 11, any suitableprocess known in the art of the electrophotography may be employed. Forexample, wet or dry methods may be employed so as to render the patternsvisible. Alternatively, the patterns may be rendered visible by frostmethods. Thus-formed visible patterns are fixed and thereaftertransferred to another copying member for storage. Furthermore, it isalso possible to electrostatically transfer the electrostatic chargeimages upon insulative layer 1 to a suitable charge-retaining member,which in turn is processed in the manner described above so as to renderthe images visible for recording.

So far the present invention has been described with references toparticularly described embodiments of electrostatic charge and visualpattem-forming processes. It should be understood that the presentinvention includes the following processes:

a. A process for forming electrostatic charge patterns comprising thesteps of: maintaining at a predetermined potential level the surface ofa face plate of the type shown in FIG. la or b; directing electron beamscontrolled by signals through thin layer electrode 3 and uponphotoconductive, layer 2 and simultaneously applying a voltage toinsulative layer 1; and directing blanket radiation upon photoconductivelayer 2, thereby forming an electrostatic charge pattern correspondingto the electron beam signals.

b. Processes comprising the steps of: maintaining at a predeterminedpotential level the surface of a face plate of the present invention,overlaying a charge-retaining recording member upon the surface of theface plate; directing electron beams controlled by signals through thinlayer electrode 3 and upon photoconductive layer 2 and simultaneouslyapplying a voltage to said recording member; and directing blanketradiation upon said photoconductive layer or removing said recordingmember from said face plate, thereby forming an electrostatic chargepattern corresponding to the beam signals.

c. Processes comprising the steps of: maintaining a charge retainingrecording member at a predetermined potential level; overlaying saidrecording member upon a face plate of the present invention, thusmaintaining the face plate at a predetermined potential level; directingelectron beams controlled by signals through thin layer electrode 3 andupon photoconductive layer 2 and simultaneously applying a voltage tosaid recording member; and directing blanket radiation upon saidphotoconductive layer or removing the recording member from said faceplate, thereby forming an electrostatic charge pattern corresponding tothe electron beam signals.

d. Processes comprising the steps of: overlaying a charge retainingrecording member upon the face plate of an electrostatic recording tubeof the present invention; maintaining the face plate at a predetemiinedpotential level; directing electron beams controlled by informationsignals through thin layer electrode 3 upon photoconductive layer 2 andsimultaneously applying a voltage to said recording member; anddirecting blanket radiation upon said photoconductive layer or removingsaid recording member from the face plate, thereby forming anelectrostatic charge pattern corresponding to the electron beam signals.

In addition to the processes described above, the present inventionfurther includes evident variations and modifications thereof insofar asthey do not have adverse effects therein.

In the above-described processes, the initial potential for maintainingthe face plate at a predetermined potential level may be a potential inthe face plate itself or an external potential applied thereto. Thepredetermined potential level may be from minus thousands of volts toplus thousands of volts. Similarly, the voltage applied simultaneouslywith the emission of electron beams may be from minus thousands of voltsto plus thousands of volts depending upon the initial potential level.

Means such as a corona discharger connected to either an AC or a DCpower supply, an electrode roller, a friction charging means, a groundedroller, etc., may be employed for applying the secondary voltage.

The electrostatic charge patterns formed in the abovedescribed processesmay be further processed by any suitable means known in the art of theelectrostatic photography so as to transfer the patterns directly orindirectly to any suitable copying material for permanent recording.

The present invention will now be described with reference to anembodiment of an electrostatic recording tube of the invention. FIG. 12illustrates the present invention as employed in hard copying" ofinformation signals, such as video signals. In FIG. 12, electrostaticrecording tube 10 includes an electron beam generafing means or electrongun comprising cathode 11, control grid 12, etc., and an electron beamemission control system comprising accelerating electrode 13, focusinggrid 14 and deflecting coil 15 all disposed in an evacuated envelope.Electrostatic recording tube 10 is provided with face plate 16 and withradiation generation means 17. As shown in FIG. 1b, face plate 16 iscomposed of four layers. On the airtight layer, 4 p. in thickness and ofhigh quality mica, an aluminum coating about 500 A in thickness isvacuum-deposited, and thereafter molten glass, having the composition of60 atomic percent of Se, 30 atomic percent of As and 10 atomic percentof S, is applied uniformly thereupon and rapidly cooled from about 280C. to room temperature so as to form a stable glass photoconductivelayer about 60 p. in thickness. Then, these layers are attached withmolten glass to a picture frame formed upon the base of the face platemade of chromium containing steel. On the free surface of the thusformed photoconductive glass a polyester film 25 p. in thickness issecured as a charge-retaining insulative layer by use of an adhesive, e.g., epoxy resin, thus providing face plate 16.

The mode of operation of recording tube 10 having face plate 16 will nowbe described. A unitary assembly including cleaner 18 composed of a furbrush, elastic rubber roller, etc., first corona discharging device 19,second corona discharging device 20 and processing device 21 composed offur brush, magnet brush, etc. is moved across the face plate to cleanthe surface thereof. Then, a voltage of 6 KV is applied to firstcharging device 19, thereby electrically charging the surface of faceplate 16 to about l,500 V. Next electron beams generated by cathode 11are accelerated by accelerating electrode 13, are focused by focusingcoil 14 and are then deflected vertically or horizontally by deflectioncoil 15. The electron beams are intensity-modulated by control grid 12of the electron gun by information signals applied thereto, and thebeams scan the surface of the face plate opposite the surface thereof towhich a voltage is applied by second discharging device 20, which ismoved in synchronism with the scanning of the electron beams. In thiscase, the slit width of second discharging device 20 is adjusted inaccordance with the spot width of the electron beam.

After the signal electron beams have scanned the whole surface of theface plate simultaneously with application of voltage by second chargingdevice 30, the whole surface of the face plate is illuminated byradiation emanating from irradiating means such as tungsten lamp 23,thereby forming a high contrast electrostatic pattern upon the faceplate. The electrostatic charge pattern is processed by processor 21 toobtain visible images. The radiation is in the form of parallel lightrays emitted from lamp 23, for example, a lOO-W tungsten lamp, throughlens system 24, and slit 25 and illuminates the portions of the faceplate previously scanned by the signal beams so as to blanketlyirradiate the photoconductive layer. Reflecting mirror 26 and airtightwall 27 are provided as indicated. This embodiment has an advantage inthat the development of the patterns formed can be immediately effectedby means of processor 21 which is assembled integrally with cleaner l8,and charging devices 19 and 20. As much as about 800 V of contrast canbe attained in the electrostatic charge patterns by applying +7 KV of DCvoltage across a discharging wire 0.06 mm in diameter where theaccelerating electrode is supplied with 30 KV after the initial chargingoperation.

The development of the formed patterns can be effected by applyingnegative toner to the patterns by means of a fur brush, thus obtaining apositive image. After development, processing mechanism 28 is disposedin close contact with the face plate for image transfer, fixing andcollecting. Copying material 29, such as paper, is placed in closecontact with face plate 16 and electrically conductive rubber roller 30,having an applied transferring bias voltage of from 1 KV to 1.5 KV, isrolled over the back surface of copying paper 29 so as to transfer thevisible image onto the front surface of copying paper 29. Thereafter,processing mechanism 28 is removed from face plate 16 and copying paper29 is wound up by rotating both paper supply reel 31 and take-up reel32. Next, the image on copying paper 29 is fixed by means of fixingmeans When 6.4 KV AC voltage is applied instead of the aforesaid DCvoltage of 7 KV for the secondary charging, a positive electrostaticcharge pattern of about 600 v can be formed.

When a negative DC voltage of KV is initially applied by coronadischarge so as to maintain the surface of the face plate at about=l,200 V and when instead of the secondary charging, a grounded metalroller is placed in close contact with the face plate so that theelectron beams scan the face plate in synchronism with the motion of theroller, thereby causing selective discharge, electrostatic contrast ofabout 500 V may be attained.

Furthennore, according to the embodiment described hereinabove,electrostatic charge patterns can be directly transferred, without thenecessity of the development thereof, after forming the electrostaticcharge patterns by initial charging, second charging whilesimultaneously scanning the face plate by electron beams carryinginformation and blanket irradiation of the face plate. This will bedescribed in more detail hereinafter. ln FIG. 12, transfer material 29,is an insulative film or paper, which is placed in close contact withthe face plate by means of conductive rubber roller 30. Thereafter, apositive voltage of 2 KV is applied to this roller and then transfermaterial 29 is removed from the face plate.

By rolling the roller over the whole surface of transfer material 29disposed in contact with the face plate, the electrostatic chargepattern thereupon is transferred to the transfer material. ln order toclosely contact the transfer material upon the face plate and thenremove the transfer material from the face plate while applying apotential thereto, feed rollers 34 and 35 of processing mechanism 28 arespaced from the face plate by approximately one centimeter and therubber roller is so disposed as to press transfer material 29 on theface plate. Thereafter, roller 30 with said potential applied thereto isrolled upon the back surface of transfer material 29. The thus-formedelectrostatic pattern is visualized, and fixed and the transfer materialis then wound around take-up reel 32.

Since the processing such as development, transfer, etc. is allperformable upon the face plate of the recording tube, full advantage isnot taken, in the above-discussed embodiment, of one of the salientfeatures of the face plate of the present invention, that is, high speedcapability. Such full advantage is taken in another embodiment of thepresent invention as will be described hereinafter with reference toFIG. 13.

Charge-retaining recording member 36 is maintained at a predeterminedpotential level by means of a pair of electrodes 42 and 42' and is movedinto contact with the face plate of the electrostatic recording tube bymeans of roller 60 and a suitable voltage is applied to the back surfaceof the recording member by means of electrode 59 in synchronism with theelectron beam scanning operation, thus forming an electrostatic chargepattern. The thus-obtained electrostatic charge pattern on recordingmember 36 is developed and transferred at station 58 spaced from theface plate while another electrostatic charge pattern is being formedupon a new portion of recording member 36 then in contact with the faceplate. Thus, high speed printing operation becomes possible in practice.

In systems for displaying input information and for reproduction ofprocessed data and stored information, the latter embodiment of thepresent invention is best suited for providing permanent images ofalpha-numerically displayed information.

The face plate used in this embodiment is fabricated in the followingmanner. Slots 5 mm in width are formed through a chromium basecontaining steel and a layer of high quality mica about 3 p. inthickness is fixed thereupon with molten glass. A coating of metallicelectrode material 500 A in thickness is applied upon the mica layer andthereafter a mixture of 75 parts of solid solution of As se obtained byheating and melting Se and As in a sealed envelope and 25 parts of solidsolution of A8283 obtained in a similar manner as described above andcontaining a small quantity of impurities such as In and Cl is vacuumdeposited upon the metallic electrode coating so as to form a glassphotoconductive layer. The thus-formed face plate is similar to the faceplate shown in FIG. 1b but has no insulative layer 1.

Such face plate is secured, with the photoconductive layer beingdirected outwardly, to an electrostatic recording tube of the typedescribed with radiation emission means 37 disposed therein. A highvoltage xenon lamp with reflecting mirror 39 is used as radiationemission means 37 and the light therefrom uniformly irradiates the innersurface of the face plate through lens system 38. Synchronizing pulsesgenerated in a reference oscillator 40 in response to input signals frommemory 44 are applied to delay circuit 41 and the signals from the delaycircuit actuate lamp 37 such that the lamp is turned on and offperiodically out of phase with application of voltage to the electrodedisposed in opposed relation to the face plate, such voltage applicationoccurring simultaneously with the signal electron beam emission.

Recording member 36 is electrically charged to a predetermined potentiallevel by means of opposed electrodes 42 and 42'. In this embodiment,recording member 36 is a synthetic insulative film made ofbidirectionally elongated ethylene, styrene or propylene macro-molecularfilm. This film is charged by corona discharge so as to have a surfacepotential of about 2,000 V and then advanced to the face plate.

Next, the character-representing electron beams are emitted at anaccelerating voltage of 25 KV and at a scanning velocity of 10 p,sec/cm, the accelerating electrode being supplied with a positivepotential. For this purpose, character or code signals are applied tothe grid electrode of the tube so as to intensity modulate generatedelectron beams and simultaneously to deflect such modulated beams topredetermined positions upon the face plate. When one line of charactersis formed upon the face plate, the electrostatic charge patterncorresponding thereto is simultaneously formed upon the recording paper.During this time, the xenon lamp is unactuated and thus not illuminated.Thereafter, at the instant of termination of the emission of thecharacter-representing electron bearns and of termination of voltageapplication by electrode 59, the out-of-phase pulse is applied to thelamp starting circuit and the lamp is illuminated for about 10 in sec.and then turned ofl.

During this irradiation, the bound, floating or stray charges in thephotoconductive layer are released, and when the recording paper moves,new positive bound charge is formed. On the other hand, that portion ofthe recording paper upon which the formed electrostatic pattern resideswith increased pattern contrast is advanced by roller 60 away from theface plate and is processed by means of the processing device at station58.

The next succeeding electrostatic pattern is formed upon the nextemission of signal beams with the simultaneous application of potentialto the recording plate.

Such synchronous operations are controlled by means of an oscillator, adelay circuit such as a flip-flop circuit and a phase-locked circuit,such as differentiating circuit. By these circuits synchronous operationof motor 43 is also controlled.

By this process electrostatic recording is effected upon recording paperof information in the form of characters. Such electrostaticallyrecorded information can be made visible by applying toner in theprocessing device of station 58 or by any other means known in theelectrostatic photography so that the record can be stored as permanentvisual record.

In the above-described embodiment, recording insulative film 36 is movedover the face plate. In this case, when a suitable surface lubricantsuch as silicon oil, teflon oil, or the like is applied to theinsulative layer or to the photoconductive layer when no insulativelayer is provided, service life of the face plate is extended. Theapplication of this surface lubricant is especially advantageous whenthe electrostatic charge pattern formed is immediately transferredthrough such liquid surface lubricant because better results will beattained.

Recording member 36 may be polyester film about 25 p. in thickness inthe form of endless belt 45 as shown in FIG. 14. Endless belt 45 isdriven by means of rollers 46 and 47 and is electrically charged to apredetermined potential level by means of charging device 48. A voltageis applied to this endless belt by electrode 51 simultaneously with theemission of electron beams upon the face plate 50 of electrostaticrecording tube 49, thereby forming an electrostatic charge pattern uponfilm 45 as in the previous embodiment.

Thereafter, the electrostatic charge pattern upon film 45 is transferredto copy member 54 driven in the direction indicated by the arrow betweensupply reel 52 and take-up reel 53. Film 45 is pressed against copymember 54 by feed roll 55. Such transferred electrostatic charge patternis developed and fixed at station 57 for permanent recording.

As described in detail hereinabove, according to the present inventionelectrostatic charge patterns having a strong exterior field and a highsurface potential difference can be formed as compared with conventionalmethods such as the method in which a pattern on a fluorescent screenplate is copied by conventional electrostatic photographic methods, themethod in which an electrostatic charge pattern is formed upon aninsulative layer by direct gaseous discharge of electron beams, etc.Further advantages of the present invention are that the sensitivity ismuch improved and that operations can be performed even in ambientlight.

What is claimed is:

l. Electrostatic image-forming apparatus comprising means operablyresponsive to information signals for emitting electron beams definingsaid image and plate means including a photoconductive layer and anelectron beam transmissive conductive base underlying saidphotoconductive layer, said base intervening said electron beam emittingbeams and said photoconductive layer, said electron beams rendering saidphotoconductive layer selectively conductive in accordance with saidimage.

2. The apparatus claimed in claim 1 including further means for applyingto said photoconductive layer blanket radiation within the range ofradiation sensitivity of said photoconductive layer.

3. The apparatus claimed in claim 1 wherein said photoconductive layeris a dispersion including cadmium sulfide and a binder material.

4. The apparatus claimed in claim 1 wherein said photoconductive layeris a dispersion including zinc oxide and a binder material.

5. The apparatus claimed in claim 1 wherein said photoconductive layerincludes chalcogenide compounds.

6. The apparatus claimed in claim 1 including further an insulativemember overlying said photoconductive layer.

7. The apparatus claimed in claim 6 including further means for applyingto said photoconductive layer blanket radiation within the range ofradiation sensitivity of said photoconductive layer.

8. The apparatus claimed in claim 7 wherein said insulative member isnon-transparent to said radiation within the range of radiationsensitivity of said photoconductive layer.

9. A process for forming an electrostatic image by using apparatuscomprising means operably responsive to information signals for emittingelectron beams defining said image and plate means including aphotoconductive layer and an electron beam transmissive conductive baseunderlying said photoconductive layer, said base intervening saidelectron beam emitting means and said photoconductive layer, saidelectron beams rendering said photoconductive layer selectivelyconductive in accordance with said image, said process comprising thesteps of:

a. overlaying an insulative member on said photoconductive layer;

b. maintaining a potential of a first polarity across said plate means;and

1. while emitting said electron beams defining said image onto saidbase, 2. applying to said plate means a field tending to eliminate saidfirst polarity potential, thereby forming said electrostatic image insaid insulative member.

10. The process claimed in claim 9 further including a terminal step ofremoving said insulative member from said photoconductive layer, therebyincreasing the contrast of said image formed in said insulative member.

11. The process claimed in claim 9 wherein said step of maintaining saidpotential of said first polarity across said plate means is practiced byapplying charge of said first polarity to said overlying insulativemember.

12. The process claimed in claim 9 wherein said step of maintaining saidpotential of said first polarity across said plate means is practiced byapplying charge of said first polarity to said insulative member priorto practice of said step of overlaying said insulative member on saidphotoconductive layer.

13. The process claimed in claim 9 wherein said step of applying to saidplate means a field tending to eliminate said first polarity potentialis practiced by applying to said plate means a potential of polarityopposite to said first polarity.

14. The process claimed in claim 9 wherein said step of applying to saidplate means a field tending to eliminate said first polarity potentialis practiced by applying alternating current corona discharge to saidplate means.

15. The process claimed in claim 9 wherein said photoconductive layerexhibits p-type semiconductivity and said first polarity is negative.

16. The process claimed in claim 9 wherein said photoconductive layerexhibits n-type semiconductivity and said first polarity is positive.

17. The process claimed in claim 9 wherein a surface lubricant isinterposed between said overlying insulative member and the surfacetherebelow.

18. The process claimed in claim 9 including the further step ofproviding an insulative layer on a surface of said photoconductive layerprior to overlaying said insulative member on said surface.

19. The process claimed in claim 18 wherein a surface lubricant isinterposed between said overlying insulative member and the surfacetherebelow.

20. The process claimed in claim 9 including the terminal step ofapplying to said photoconductive layer blanket radiation within therange of sensitivity of said photoconductive layer, thereby increasingthe contrast of said image formed in said insulative member.

21. The process claimed in claim 20 including the further step oftransferring said electrostatic image to a copying member.

22. The process claimed in claim 21 including the further step ofvisualizing said transferred electrostatic image on said copying member.

23. The process claimed in claim 22 including the further step of fixingsaid visualized image on said copying member.

24. The process claimed in claim 20 including the further step ofvisualizing said electrostatic image on said insulative member.

25. The process claimed in claim 24 including the further step oftransferring said visualized image to a copying member.

member.

27. The process claimed in claim 24 including the further step of fixingsaid visualized image on said insulative member.

(SEAL) Attest:

McCOY M. GIBSON .JR. c. MARSHALL DANN Attesting Officer Commissioner ofPate nts UTTI ED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatentNo. 3,673,595 v I Dated June27 1972 Inventor(s) Eiichi Inoue et-81.

It is certified that error app earsin the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

' Item [73], Titlepage, "Canon Camera Kabushiki Kaisha should read--Canon Kabushiki Keishacol; 3, line 39 "not" should read --no--. 3.,line 'e'tf'iPFFfig'fri-ih0 d read --anthracene--.

Col'. 4, line 14, "adsorbed" should read --absorbed--.

139 l 7.19;. ar,'r' rshv uldumread.rriur Col. 9, li e ehould readSignedand sealed this-14th day of January 1975.

(mm Po-1050 (10-69) uscoMM-Dc 60376-P69 U.S. GOVERNMENT PRINTING OFFICE:1969 0-366-334 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION-Patent No. 3,673, 595 v Dated June 27 1972 Ihventor(s) Eiichi Inoue eta1.

It is certified that errer appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Item [73] Titlepage, "Canon Camera Kabushiki Kaisha" 7 should read--Canon Kabushiki Kaisha-- Col; 3, line 39, "not" should read --no--.

Col. 3,

line ??%9ep.'v'..ho d ead --anthracene--.

Col. 4, line l-4, "adsorbed" should read "absorbed".-

.LCQ ,uwlsi sm79 'V' r". sh ulslnreraslnrziur U C 01. 9, lirle shoulread "7' V--.

Signed and sealed this 14th day of January 1975.

(SEAL) Attest:

McCOY M. GIBSON JR. 0'. MARSHALL DANN Attesting Officer Commissioner ofPatents PC4050 USCOMM-DC scams9 US. GOVERNMENT PRINTING OFFICE: 9690-366335

2. applying to said plate means a field tending to eliminate said firstpolarity potential, thereby forming said electrostatic image in saidinsulative member.
 2. The apparatus claimed in claim 1 including furthermeans for applying to said photoconductive layer blanket radiationwithin the range of radiation sensitivity of said photoconductive layer.3. The apparatuS claimed in claim 1 wherein said photoconductive layeris a dispersion including cadmium sulfide and a binder material.
 4. Theapparatus claimed in claim 1 wherein said photoconductive layer is adispersion including zinc oxide and a binder material.
 5. The apparatusclaimed in claim 1 wherein said photoconductive layer includeschalcogenide compounds.
 6. The apparatus claimed in claim 1 includingfurther an insulative member overlying said photoconductive layer. 7.The apparatus claimed in claim 6 including further means for applying tosaid photoconductive layer blanket radiation within the range ofradiation sensitivity of said photoconductive layer.
 8. The apparatusclaimed in claim 7 wherein said insulative member is non-transparent tosaid radiation within the range of radiation sensitivity of saidphotoconductive layer.
 9. A process for forming an electrostatic imageby using apparatus comprising means operably responsive to informationsignals for emitting electron beams defining said image and plate meansincluding a photoconductive layer and an electron beam transmissiveconductive base underlying said photoconductive layer, said baseintervening said electron beam emitting means and said photoconductivelayer, said electron beams rendering said photoconductive layerselectively conductive in accordance with said image, said processcomprising the steps of: a. overlaying an insulative member on saidphotoconductive layer; b. maintaining a potential of a first polarityacross said plate means; and c.
 10. The process claimed in claim 9further including a terminal step of removing said insulative memberfrom said photoconductive layer, thereby increasing the contrast of saidimage formed in said insulative member.
 11. The process claimed in claim9 wherein said step of maintaining said potential of said first polarityacross said plate means is practiced by applying charge of said firstpolarity to said overlying insulative member.
 12. The process claimed inclaim 9 wherein said step of maintaining said potential of said firstpolarity across said plate means is practiced by applying charge of saidfirst polarity to said insulative member prior to practice of said stepof overlaying said insulative member on said photoconductive layer. 13.The process claimed in claim 9 wherein said step of applying to saidplate means a field tending to eliminate said first polarity potentialis practiced by applying to said plate means a potential of polarityopposite to said first polarity.
 14. The process claimed in claim 9wherein said step of applying to said plate means a field tending toeliminate said first polarity potential is practiced by applyingalternating current corona discharge to said plate means.
 15. Theprocess claimed in claim 9 wherein said photoconductive layer exhibitsp-type semiconductivity and said first polarity is negative.
 16. Theprocess claimed in claim 9 wherein said photoconductive layer exhibitsn-type semiconductivity and said first polarity is positive.
 17. Theprocess claimed in claim 9 wherein a surface lubricant is interposedbetween said overlying insulative member and the surface therebelow. 18.The process claimed in claim 9 including the further step of providingan insulative layer on a surface of said photoconductive layer prior tooverlaying said insulative member on said surface.
 19. The processclaimed in claim 18 wherein a surface lubricant is interposed betweensaid overlying insulative member and the surface therebelow.
 20. Theprocess claimed in claim 9 including the terminal step of applying tosaid photoconductive layer blanket radiation within the range ofsensitivity of said photoconductive layer, thereby increasing thecontrast of said image formed in said insulative member.
 21. The processclaimed in claim 20 including the further step of transferring saidelectrostatic image to a copying member.
 22. The process claimed inclaim 21 including the further step of visualizing said transferredelectrostatic image on said copying member.
 23. The process claimed inclaim 22 including the further step of fixing said visualized image onsaid copying member.
 24. The process claimed in claim 20 including thefurther step of visualizing said electrostatic image on said insulativemember.
 25. The process claimed in claim 24 including the further stepof transferring said visualized image to a copying member.
 26. Theprocess claimed in claim 25 including the further step of fixing saidtransferred visualized image on said copying member.
 27. The processclaimed in claim 24 including the further step of fixing said visualizedimage on said insulative member.